The present invention relates generally to a machine for throwing, pitching or otherwise propelling spherical objects such as baseballs, softballs, tennis balls or the like. More particularly, the present invention relates to a ball feeding and locating system that ensures that all of the balls thrown will be released consistently. The present invention is an improvement of the invention disclosed in U.S. Pat. No. 4,195,614, which is incorporated herein by reference.
A wide variety of ball throwing machines have been used in the past for activities such as batting and tennis practice. The early ball throwing machines typically employed swing arms, spring loaded mechanisms or simple mechanical impact plates to propel the balls. However, such devices experience considerable difficulty controlling the ball to obtain uniform throws. Additionally, such prior art machines can only throw "straight" balls and were incapable of throwing a ball with either a side spin or top spin. Thus, in the field of baseball, such a machine has the drawback of not being able to throw curves or sliders. Similarly in sports such as tennis, they are incapable of delivering balls with any significant top spin.
More recently ball throwing devices employing two counter-rotating wheels to propel the ball have become known in the art. For example, U.S. Pat. No. 4,195,614 discloses a ball throwing machine having a pair of rotating discs supported for rotation in angularly opposed relation so as to laterally engage a ball for propulsion. The machine disclosed in the '614 patent also contemplates rotating the discs at different speeds, thereby placing a sidespin on the ball. Thus, the ball throwing machine is able to throw "curves" or "sliders". The rotating wheels include concentric depressed angular grooves which serve to locate the radial position of the ball on the wheels themselves, thereby ensuring that the ball is consistently released from the same point. It is, of course, essential that the ball be released at the same point in order to ensure accurate control of its trajectory. While the '614 device is extremely effective, its one drawback is that the angular grooves cause the rotating discs to be relatively expensive to manufacture. Therefore, there is a need for a mechanism that is inexpensive to manufacture, yet capable of accurately positioning a ball within the environment of a pair of rotating discs to ensure that the ball is released at a consistent position.
Accordingly, it is a general objective of the present invention to provide a ball throwing machine that is capable of simulating most of the ball trajectories experienced in the actual playing of baseball, softball, tennis and other activities wherein the controlled propulsion of a ball or other similar spherical object is encountered. To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a ball projective apparatus is provided that includes a pair of rotary ball-contacting discs having angularly opposed, substantially planar ball engaging surfaces whose spacing varies between a maximum distance greater than the diameter of the ball and a minimum distance no greater than the ball's diameter. A rotary means is provided to rotate the ball contacting members, and a pair of positioning discs precisely control the tangential release position for throwing the ball. The positioning discs are positioned co-axially with the ball contacting discs on their contact surfaces.
In accordance with an additional aspect of the invention, the rotary speed of the two ball contacting members can be different so as to impart a lateral spin to the propelled ball.
Preferably, the ball projecting apparatus also includes a feed chute having a biasing means such as a leaf spring for urging the balls to contact the positioning disks at a radial position that is before the position at which the natural geometry of the opposed ball contacting discs would force such contact.